Long-term Caspian Sea level variations based on the ERA-interim model and rivers discharge

In this research, precipitation-evaporation is studied based on the ERA-Interim model of ECMWF in order to estimate changes in the Caspian Sea (CS) level and the validity of the results is evaluated in a period between 1980 to the end of 2015. Recorded data about the rivers entering the CS were also studied for better prediction of changes in water level. According to satellite images and software analyses, in average, evaporation has increased with a rate of 0.89?km(3)/year, while precipitation and rivers discharge have decreased by the rates of 1.09 and 1.41 km(3)/year, respectively during the 36 years. The standard deviation of the sea level changes caused by Volga discharge (normally entering 249.13?km(3)/year into the sea alone) is closer to the recorded standard deviation obtained from the change of the CS level than the other two factors. Also, the lowest and the highest correlation coefficients relative to the recorded sea level changes were calculated considering the simultaneous effect of precipitation-evaporation and simultaneous effect of all parameters, respectively. As a conclusion, it can be said that the main reason for decreasing the CS level during recent years could be attributed to the rise of evaporation in comparison to precipitation and inlet rivers' discharges.